HOW TO STORE OLIVE OIL
Olive oils are not as stable as vegetable oils with a high saturated fat content such as coconut or palm oil and therefore their storage requires special care. However, thanks to their high monounsaturated fat content, olive oil can be stored longer than most other oils with a higher content of polyunsaturated fat - as long as it's stored properly.
When choosing your storage location, remember that heat, air, and light are the enemies of oil. Exposure to these elements will increase the likelihood of oxidation which will make the oil taste rancid.
Any oil container should have a lid or airtight cap to keep out unwanted air which will cause oxidation.
Constant opening and closing of the container will also expose the oil to air. Therefore it is much better to pour oil from a larger container into a smaller one that you can use for normal, regular consumption. In Spain, the typical container for everyday use is a metal kettle with a very long, narrow spout which stops air from entering the container.
PROTECT FROM LIGHT
The best storage containers for olive oil are made of either coloured glass (to keep out light) or a non-reactive metal, such as stainless steel. Avoid plastic where possible as the oil can absorb polyvinyl chlorides (PVCs).
If you only have clear containers for the oil, you should keep these boxed or stored in a dark cupboard.
Temperature is also important in preventing degradation of olive oil. It is generally recommended to store olive oil at room temperature (18-22°C) in a dark, cool cupboard away from the oven or other heat-producing appliances.
If your kitchen is routinely warmer than that, you can refrigerate the oil. When refrigerated, olive oil will solidify and have a buttery consistency. Returning it to room temperature restores its fluidity and colour.
Olive oil will keep well if stored in a sealed container in a cool, dark cupboard for about one year. If unopened, the oil may keep for as long as two years depending on the content of antioxidants.
However, unlike a fine wine, olive oil does not improve with age. As it gets older, olive oil gradually breaks down - the acidity increases and the flavour weakens. Eventually, the oil will oxidise and become rancid.